<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>

    <style>
        .isOne {
            color: red;
        }
    </style>

</head>

<body>


    <div id="box">
        <span :class="{isOne:isOnes}">{{html}}</span>
        <button v-on:click="classCon">按钮</button>
    </div>

</body>

<script src="https://cdn.bootcss.com/vue/2.6.11/vue.js"></script>
<script>
    new Vue({
        el: '#box',
        data: {
            html: '啦啦啦',
            isOnes: true,
            isTwo: true,
        },
        methods: {
            classCon: function() {
                this.isOnes = !this.isOnes;

            }
        }
    })
</script>

</html>